Apparatus for the uttlization of combustible waste gases of refineries or other plants



0d. 22, 1968 BAUER L 3,406,895

APPARATUS FOR THE UTILIZATION OF COMBUSTIBLE WASTE GASES 0F REFINERIES OR OTHER PLANTS Filed March 2, 1966 UQ iCd S ate Pat imjo APPARATUS FOR THE UTILIZATION OF COM- BUSTIBLE WASTE GASES F REFINERIES OR OTHER PLANTS Erich Bauer, Eggendorf, and Franz Reichard, Vienna,

Austria, assignors to Osterreichische Miueralolverwaltung Aktiengesellschaft, Vienna, Austria Filed Mar. 2, 1966, Ser. No. 531,255 Claims priority, application Austria, Mar. 18, 1965, A 2,483/65 4 Claims. (Cl. 230-6) ABSTRACT OF THE DISCLOSURE The process and apparatus enable combustible oil refinery waste gas, which is yielded at low super-atmospheric pressure, to be introduced into a fuel gas pipe. The waste gas is sucked from the waste gas pipe by a compressor and after its pressure has been'increased by the compressor, the gas is introduced into a fuel gas pipe. To prevent air from mixing with the waste gas and forming an explosive mixture, the pressure in the waste gas pipe is maintained above atmospheric pressure by varying the suction capacity of the compressor. In addition, a torch installation is provided to dispose of any excess waste gases should the amount of waste gas exceed the capacity of the compressor.

effect of alarming the environment. Besides, however,

the calorific value of these gases is destroyed in the torch so that discharging of the waste gases by way of the torch represents a loss which might be considerable in refineries. It already had been suggested to collect these combustible waste gases at least partially in a gasometer and to conduct them from there to a fuel gas supply net. However, construction and maintenance of a gasometer serving this purpose frequently involves expenditure impairing the economy of the waste gas utilisation.

The present invention now aims at eliminating these drawbacks and is essentially characterized in that the waste gases are being sucked from the waste gas pipes and that the suction pressure is limited to a minimum value being equal to or higher than the atmospheric pressure. Connecting the waste gas pipe to the suction side of a compressor entails the danger that in the case of a low waste gas yield the waste gas pipe is completely sucked empty. As soon as the pressure in the waste gas pipe decreases below the atmospheric pressure, the danger arises that through leakages air is being sucked into the waste gas pipe thus forming together with the combustible waste gases an explosive mixture, which represetns a considerable danger. But by limiting the suction pressure to a minimum value being at least equal to the atmospheric pressure this danger is eliminated, since under any working conditions penetration of air is prevented. It therefore is made possible to withdraw the waste gases directly from the waste gas pipe, thereby avoiding the use of an expensive gasometer, and to compress them to a pressure higher than the pressure in the fuel gas supply net, so that the waste gases may be introduced into the fuel gas pipe.

Most frequently waste gases are yielded under com 3,406,895 Patented Oct. 2 2, 1 968 paratively low super-atmospheric pressure in the Waste gap pipe. Thus the suction pressure of the compressor has to be limited to a value which is below the average pressure of the waste gas pipe, but by no means below the atmospheric pressure. When limiting the suction pressure to a minimum value being equal to the atmospheric pressure penetration of air into the waste gas pipe is eliminated, however a, certain tolerance of the control has to be taken into consideration, and a comparatively low super-atmospheric pressure in the waste gas pipe is appropriate for guaranteeing the necessary security against penetration of air. The minimum value to which the suction pressure of the compressor is limited may, according to the invention, appropriately range between 40 and 200 mm. water column, preferably being about mm. water column. Being waste gases, the yield of the waste gases varies greatly. In case of a Working trouble of the plant the waste gas yield may be a multiple of the waste gas yield at normal operation. It seems appropriate to outline the compressor for normal operation, and expenses for outlining the compressor for extreme cases are not justified. In case of a waste gas yield exceeding the compressor capacity, however, the superfluous waste gases may, according to the invention, be discharged by Way of a torch installation known per se in oil refineries.

Usually 'waste gases include also liquid components which, e.g. in refineries operating with a torch installation, are separated and recovered in a liquid separator. However, in this case also the yield of liquid components in the waste gas pipe may be extremely high in the case of working trouble. Thus, in order to meet the danger that in the case of such an extreme yield in liquidthis liquid invades the operating compressor thereby causing damage to the compressor or that an undesired pumping of the liquid into the fuel gas pipe occurs, according to the present invention the liquid level of a liquid separator installed into the waste gas pipe on the suction side of the compressor may be controlled and in the case of an increase of the liquid level over a predetermined height the compressor may be stopped or an alarm equipment may be actuated.

A device for carrying out the inventive process is essentially characterized by at least one pressure sensitive control unit exposed to the pressure on the suction side of the compressor, which unit serves to control the'suction capacity of the compressor. For guaranteeing greater security the employment of a plurality of a pressure sensitive control units operating simultaneously in the same sense is to be recommended. However, within the scope of the present invention also at least two pressure sensitive control units may be exposed to the pressure present on of the other control unit is set, this lower pressure, however, still being higher than the atmospheric pressure. In this case those control units, the switching points of which are set to the lower pressure value, only are operating, if those pressure sensitive units, the switching points of which are set to the higher pressure value, are failing to work or if the control of the compressor capacity elfected by these units is insufiicient. The compressor capacity may be changed in various ways. According to the invention an arrangement may be elected in which the pressure side of the compressor is connected to the suction side of the compressor by means of a short-circuit, to which an adjustable throttle valve is fitted which is controlled by at least one of the pressure sensitive control units. The depressors or a change of the position of the guide or rotary blades in the case of turbo compressors effected by these units. Finally, at least one of the pressure sensitive control units may control the control switch of the driving motor thereby completely stopping the compressor or reducing its speed. When using a plurality of pressure sensitive control units, the switching points of which are set to differently high pressures, these control units set to various pressures may carry out various controlling tasks. Thus e.g. the control unit or units, the switching point of which is set to a lower pressure, may stop the driving motor of the compressor, while the control unit or units, the switching point of which is set to a higher pressure, may control the delivery capacity of the compressor. Thus it is safeguarded that in case the change of the suction capacity of the compressor is insuflicient to maintain a predetermined minimum pressure in the waste gas pipe a dangerous sub-atmospheric pressure in the waste gas pipe is, by all means, avoided by completely arresting the compressor.

In the drawing attached the present invention is described for the use in an oil refinery by means of embodiments, FIGURES 1, 2 and 3 showing different diagrams.

In the diagram according to FIGURE 1 numeral 1 is the waste gas pipe leading over a water closure 25 to the torch 26. This water closure 25, on the one hand, serves as check valve preventing penetration of air from the torch installation 26 into the waste gas pipe 1, and, on the other hand, as valve maintaining the pressure. Height a of the water column determines the upper pressure limit in the waste gas pipe 1. To a point of the waste gas pipe 1 lying before the water closure 25 the suction pipe 3 of the compressor 4 is connected, a liquid separator 2 being interconnected. Numeral 5 designates the pressure side of the compressor, numeral 6 the driving motor of the compressor and numeral 7 its supply for electric current. The pressure side 5 of the compressor is connected to the suction side 3 by means of a shortcircuit 8 into which again an adjustable throttle valve 9 is fitted. Numeral 10 designates a pressure sensitive control runit which is exposed, on the one hand, to the pressure present on the suction side 3 of the compressor or in the waste gas pipe 1 (line 11) and, on the other hand, to the atmospheric pressure (line 12). This pressure sensitive control unit 10 acts on the throttle valve 9 opening it when a predetermined pressure value is reached, so that the suction capacity of the compressor decreases.

To the suction side 3 of the compressor and, respectively, to the waste gas pipe 1 two pressure gauges 13 and 14 are connected which actuate switches 15 and 16, respectively, arranged in the current supply of the motor 6 and interrupting the current supply of the motor 6 when a predetermined value of the suction pressure has not been reached. The switching point of the manometer 14, e.g., may be set to a lower pressure than the switching point of the manometer 13, so that generally only the manometer 13 is in operation.

In the liquid separator 2 a float 17 is indicated, which float controls a switch 18 in the current supply of the motor 6 and stops the motor and thus the compressor when a predetermined liquid level has been exceeded.

Numeral 19 designates the pressure pipe of the compressor to which pipe a check valve 20 opening in the flow direction is connected to prevent a reflow of gas from: the fuel gas pipe, into which runs the pressure line 19, to the compressor 4.

In the diagram according to FIGURE 2 a pressure sensitive unit 21, which again is exposed to the suction pressure and, on the other hand, may be exposed to the atmospheric pressure, controls a control switch 22 controlling the speed of the driving motor 6 and thus of the compressor 4.

In the arrangement according to FIGURE 3 the pressure sensitive unit 23 controls the delivery capacity of the compressor 4 by means of a control link 24. With piston compressors the piston stroke and with turbo compressors the position of the guide or rotary blades may be changed accordingly by means of the control link 24.

What we claim is:

1. An apparatus for the utilization of oil refinery waste gases yielded under low super-atmospheric pressure comprising: a waste gas pipe, a discharge conduit, a motor actuated compressor means having a suction side and discharge side disposed intermediate said pipe and said conduit, said suction side of said compressor in communication with said waste gas pipe, said discharge side of said compressor in communication with said discharge conduit, a torch installation connected to said waste gas pipe for discharging and burning superfluous waste gases when said waste gas yield in said waste gas pipe exceeds the capacity of said compressor, a liquid separator incorporated in said Waste gas pipe, pressure sensitive means measuring the pressure in said waste gas pipe and cooperating with control means controlling said motor of said compressor so that in case the pressure in said waste gas pipe falls under a first predetermined value said motor is stopped, safety pressure sensitive means measuring the pressure in said waste gas pipe and coopcrating with said control means controlling said motor of said compressor so that in case the pressure in said waste gas pipe falls under a second predetermined value being below said first predetermined pressure value but above atmospheric pressure said motor is also stopped, and a check valve in the discharge conduit preventing a back flow of said waste gases to said compressor.

2. An apparatus for the utilization of oil refinery waste gases yielded under low super-atmospheric pressure comprising: a waste gas pipe, a discharge conduit, a motor actuated compressor means having a suction side and discharge side disposed intermediate said pipe and said conduit, said suction side of said compressor in communication with said waste gas pipe, said discharge side of said compressor in communication with said discharge conduit, a torch installation connected to said waste gas pipe for discharging and burning superfluous Waste gases when said waste gas yield in said waste gas pipe exceeds the capacity of said compressor, a liquid separator incorporated in said waste gas pipe, means for preventing liquid in said separator from being drawn into said compressor, pressure sensitive means measuring the pressure in said waste gas pipe, control means for controlling said motor of said compressor in dependence on the pressure in said waste gas pipe as measured by said pressure sensitive means, and a check valve in said discharge conduit preventing back flow of said waste gases to said compressor.

3. An apparatus for the utilization of oil refinery waste gases yielded under low super-atmospheric pressure comprising: a waste gas pipe, a discharge conduit, a motor actuated compressor means having a suction side and discharge side disposed intermediate said pipe and said conduit, said suction side of said compressor in communication with said waste gas pipe, said discharge side of said compressor in communication with said discharge conduit, a torch installation connected to said waste gas pipe for discharging and burning superfluous waste gases when said waste gas yield in said waste gas pipe exceeds the capacity of said compressor, a liquid separator incorporated in said waste gas pipe, pressure sensitive means measuring the pressure in said waste gas pipe, control means for controlling said motor of said compressor in dependence on the pressure in said waste gas pipe as measured by said pressure sensitive means, said liquid separator being provided with means for measuring the liquid level, said means for measuring the liquid level being connected to said control means of said motor to stop said motor when a predetermined liquid level has been exceeded, and a check valve in said discharge conduit preventing back flow of said waste gases to said compressor.

4. An apparatus for the utilization of oil refinery waste gases yielded under low super-atmospheric pressure comprising: a waste gas pipe, a discharge conduit, a motor actuated compressor means having a suction side and discharge side disposed intermediate said pipe and said conduit, said suction side of said compressor in communication with said waste gas pipe, said discharge side of said compressor in communication with said discharge conduit, a torch installation connected to said Waste gas pipe for discharging and burning superfluous waste gases when said waste gas yield in said waste gas pipe exceeds the capacity of said compressor, a liquid separator incorporated in said waste gas pipe, pressure sensitive means measuring the pressure in said waste gas pipe, control means for controlling said motor of said compressor in dependence on the pressure in said waste gas pipe as measured by said pressure sensitive means, said liquid separator being provided with means for measuring the liquid level, said means for measuring the liquid level being connected to an alarm means which is actuated when a predetermined liquid level has been exceeded, and a check valve in said discharge conduit preventing back fiow of said waste wases to said compressor.

References Cited UNITED STATES PATENTS 10 2,295,775 9/1942 Crittenden 23018 2,899,013 8/1959 Carter 230-17 3,115,296 12/1963 Karwat 23017 3,229,895 1/1966 West et al. 23021 15 WILLIAM L. FREEH, Primary Examiner. 

